US3261496A - Floating roof tank seal - Google Patents

Description

July 19, 1966 w. E. JooR u FLOATING ROOF TANK SEAL 5 Sheets-Sheet l INVENTOR. W////c7/77 f. foo/,l

ATTRIVEV July 19, 1966 w. E. JooR n 3,261,496

FLOATING ROOF TANK SEAL Filed Nov. 2l, 1962 5 Sheets-Sheet 2 INVENTOR. W//am E. foo/,Z

ATTORNEY July 19, 1966 w. E. Joon 3,261,496

FLOATING ROOF TANK SEAL Filed Nov. 21, 1962 s sheets-sheet s INVENTOR. l/V//Q/n f'. Joa/,

l BY n J Z/@Wyyw ATTO/PN United States Patent 3,261,496 FLOATING RQF TANK SEAL William E. .loor Il, Houston, Tex., assigner to Wyatt Industries Inc., Houston, Tex., a corporation of Texas Filed Nov. 21, 1962, Ser. No. 239,140 7 Claims. (Cl. 22d- 26) This invention relates to floating roof tanks, particularly for volatile fluid products, and consists more particularly in novel means for sealing the sometimes irregular clearance space necessarily provided between the confronting side wall of the roof and the tank shell.

One disadvantage in present types of floating roof tanks is that the sealing means requires that the roof remain telescoped within the tank shell. Accordingly, the maximum capacity of the tank is reduced by the volume of the submerged roof parts. Another disadvantage is that, by making the shoes vertically substantially co-extensive with the roof side wall a very large amount of expensive sealing diaphragm material must be provided. Still another disadvantage of current tank seals of the above type results from the difficulty of assembling and disassembling the sealing parts with the tank and roof.

Accordingly, an object of the present invention is to provide floating roof tank seal means which permits the roof to be projected substantially above the upper edge of the tank shell to thereby substantially increase the maximum capacity of the tank.

Another object is to substantially simplify the means for supporting and outwardly |biasing the shoes which slidably connect the sealing fabric to the tank shell or wall.

Another object is to substantially reduce the vertical expanse of the shoes and thereby decrease the quantity of sealing fabric which must be provided to completely seal the clearance space between the roof and tank shell.

Another object is to provide improved, greatly simplified -means for assembling and disassembling the sealing means in the clearance space between the floating roof and the tank shell.

Another object is to provide novel anti-rotation means for a oating roof which incorporates a tank overflow.

Still another object is to provide centering means for a floating roof.

Another obje-ct is to provide means to increase the stability and vapor sealing properties of a floating roof, particularly of the pontoon type.

These objects and others hereafter appearing are attained by the structure herein disclosed and claimed which consists generally of a sealing diaphragm traversing the clearance space between the roof and the tank shell and secured to an annular series of relatively narrow plate-like shoes arranged circumferentially around and engaging the inner face of the shell. The diaphragm material hangs downwardly along and completely covers the inner faces of the shoes and traverses the clearance between adjacent ends thereof. Vertically disposed, quarter-elliptic lower leaf springs are secured to the lower part of the roof wall and extend outwardly and upwardly to the vicinity of and slidably engage the lower portions of the shoes to bias the shoes outwardly against the tank shell. Upper, vertically disposed leaf springs are secured at their foot portions to the roof side wall slightly above the sealing diaphragm and have elements secured to and resiliently biasing the upper portions of the shoes against the shell. The upper leaf springs have additional elements which, normally, bear resiliently against the tank shell above the shoes and which support a weather shield. When it is desired to remove the seal, it is simply necessary to unbolt the inner edge of 3,25l,496 Patented July 19, 1966 ICC the sealing diaphragm material from the roof wall, whereupon the sealing parts can be withdrawn bodily from their clearance space between the roof and tank shell. An upright pipe extending from the tank floor through the roof is braced to the upper edge of the tank wall and has an overflow opening positioned just above the maximum normal level of liquid in the tank. Resilient centering devices project radially from the bottom of the roof and bear against the tank wall. A skirt depends from the periphery of the roof to prevent the escape of product vapors in case of minor tilting of the roof.

In the accompanying drawings,

FIG. 1 is a vertical transverse section through a portion of a tank shell and floating roof of the pontoon type illustrating the novel sealing means and its biasing and support structures.

FIG. 2 is a view similar to FIG. 1, but showing the roof propelled upwardly substantially beyond the upper edge of the tank shell.

FIG. 3 is an inside view of a portion of the sealing structure and is taken substantially on line 3 3 of FIG. 1.

FIG. 4 is a vertical transverse sectional view of a modification.

FIG. 5 is an elevation of the centering device.

FIG. 6 shows in vertical transverse section the improved anti-rotation and overflow feature.

The tank shell shown in FIGS. 1 and 2` is built up of vertically assembled plates 7 and 8 riveted along their overlapping seams, as at 9. The floating roof shown is of the pontoon type having a vertical cylindrical side wall 10, a floor or bottom wall 11, and a top wall 12. The side wall extends below bottom wall 11 to form a skirt 13.

Engaging and extending circumferentially around the inner face of the tank shell, formed by riveted or welded plates 7 and 8, are a plurality of plate-like, generally rectangular shoes 15, the abutting ends of which are slightly spaced apart, as shown in FIG. 3, to accommodate slight irregularities in the contour of the tank shell. The upper and lower edges of the shoes are angled inwardly, as at 16 and 17, to facilitate the -riding of the shoes Vover the seams between joined plates and any other irregularities in the tank shell during vertical sliding of the shoes therealong. The lower portions of the shoes are biased outwardly against the tank wall by means of an annular series of vertically disposed, quarter-elliptical leaf springs 18 which, at their lower extremities, are bolted, as at 19, to the roof skirt 13 near the lower edge thereof. These lower leaf springs extend upwardly and outwardly to the vicinity of the lower portions of the shoes and each spring, near its upper end, slidably bears against an angle slip 20 secured to the inwardly tapered lower part 17 of the shoe |by means of bolts 21. Thus, the lower springs 18 are free to flex and slide on clips 2f?, as necessary due to variations in the contour of the tank shell, while continuously urging the shoes into engagement with the tank shell.

Secured to the inclined upper edges 16 of the shoes are vertically disposed spring strap members 24 each hauing an angled foot 25 at its upper extremity riveted to the intermediate portion of an upper shoe supporting spring strap 26. The lower extremity or foot of each strap 26 is snugly received in a pocket formed between the roof side wall 10 and a small plate 27 which is welded or otherwise secured to the roof wall. The lower edge of pocket forming plate 27 is bent inwardly, as at 28, to close the bottom of the pocket. A nut 29 is welded to the outer face of plate 27 and the plate, as well as the lower part of spring strap 26 in alignment with the nut are apertured for receiving a locking bolt 30 which is threaded into the nut and abuts the roof wall at its inner end. This aperture 31 in the spring strap 26 is of ample size to accommodate dimensional variations. Bolt 30, therefore, prevents withdrawal of the spring strap 26 from its securing pocket.

Strap 26 extends outwardly and upwardly beyond branch strap 24 to form an outwardly bowed knee 33 which, in the lower positions of the roof, bears resiliently against the linner face of the tank shell, and thence extends inwardly and upwardly as at 34. The upper extremity of portion 34 is bent over, as at 35, for attachment, as by means of a bolt 36, to the sun and rain shield 37. Shield 37 has a downwardly bent inner edge 38 which slides upon the upper wall 12 of the roof. Strap 24 andthe lower part of spring strap 26, therefore, form an inverted Y, the legs of which are drawn together in the assembly so as to resiliently urge the lupper portion of the attached shoe against the inner face of the tank shell. Similarly, the bowed, knee-forming portions of leaf springs 26 are distorted inwardly in the assembly so that the straps will bear resiliently against and be confined within the tank wall.

A continuous sheet of flexible diaphragm sealing material has a slack portion 40 bolted along its inner edge to a ange 41 formed on the roof side wall. Portion 40, `at its outer edge, is folded and secured by means of lower bolts 23 and bolting straps 42 to the upper portions of shoes 15. The diaphragm material then hangs downwardly, as at 43, along the inner faces of the shoes and, at its lower edge, is secured by bolts 21, upon which bearing clips 20 are mounted, and clamping bars 44 to the lower portions of the shoes. Sheeting of ber glass, nylon, Daeron, or asbestos, coated on both sides with polyurethane has been found to be exemplary for this purpose.

FIG. 2 shows the floating roof lifted to approximately its maximum elevated position with respect to the tank shell. In this position of the roof, shoes 15 may extend slightly above the edge 46 of the tank shell and the bowed and extreme upper portions 33, 34 of leaf spring members 26 project above and outwardly beyond the shell. However, the expansive force of lower leaf springs 18 as well as upper spring structures 24, 26 insure continued proper biasing of the shoes outwardly against the inner face of the tank shell. Thus, the maximum capacity of the tank is substantially greater than is the case with present styles of floating roofs and seals which prevent the roof from being lifted substantially above the tank shell. Upon receding of roof downwardly into the tank, locking bolts 36 prevent the withdrawal of the leaf springs 26 from pocket forming parts 27 due to frictional dragging of the shoes on the tank shell. However, in the position of FIG. 1, the lateral stressing of the upper leaf springs 26 will create suicient binding within the pockets to prevent these springs from being drawn therefrom.

In assembling the seal structure with a tank and floating roof, the upper leaf springs 26, 24, with shoes 15 and the flexible diaphragm structure already secured thereto first will be lowered into the clearance space between the roof and tank shell. It will, of course, be necessary to spring together leg portions 24, 26 of the upper leaf springs to permit this. The lower extremities of leaf springs 26 are slid into pocket forming parts 27 and locking bolts 30 applied. Next, spring legs 24, 26 will be released and the inner edge of sealing material portions 40 will be bolted to ilange 41. Finally, lower leaf springs 18 may be bolted in their positions so as to resilicntly bias the lower portions of the shoes against the tank shell. Alternatively, these lower springs may be applied rst and flexed inwardly to permit dropping of the shoes into place. The entire seal structure may be withdrawn as a unit, lif desired, simply by reversing the assembly procedure.

In the modification in FIG. 4, a leaf spring 50, similar to leaf springs 26, 33, 34 of the lirst form, has its lower extremity 51 secured in the pocket formed by a plate part 52 and locked in position by a bolt 53, as before. The spring strap is laterally stressed iin assembly, so that its knee 54 will bear resiliently against the inner face of tank shell 55. A weather shield 56 is supported on the upper extremities of the leaf springs 50, 54. However, in this form, the seal is provided by means of a torofidal bag 58 of suitable impervious flexible sheeting material which is partially filled by a distending iluid, preferably a liquid, as at 59. This will cause the bag walls 6) and 61 to bear resiliently against the opposing tank shell and roof wall and also will cause outer bag wall 61 to bear slidably against the inner face of the tank shell. The bag is supported by vertical hangers 62 which are bolted to a circumferential bar or bars 63 in turn secured to the upper edges of the bag walls by means of bolts 64. Hangers 62 are pivotally suspended from pivots 65 projecting from reinforcing members 66 secured intermediately to leaf springs 50.

FIGS. 4 and 5 illustrate one of several novel centering mechanisms arranged symmetrically about the roof and which may be used with the rst form also. This mechanism includes a tubular casing with a larger part 68 and a smaller part 69 radially and rigidly supported from the roof bottom plate 70 by means of brackets 71 and 72. A shaft 73 carries a bearing wheel 74 at its outer end for riding on the tank shell. The shaft extends slidably rinto the tubular casing and at its inner end has an externally threaded head 75. A coiled tension spring 76 is threaded at its inner end on head and at its outer end on a similarly threaded sleeve 77 lodged in the outer end of larger housing part 68 about shaft 73. Spring 76 therefore urges shaft 73 and its bearing wheel outwardly against the tank wall. Outward movement of shaft 33 is limited by a pin 78 extending across casing part 69 and through a slot 79. The several mechanisms cooperate to resiliently center the roof and to limit the radial stresses applied to the seal parts.

FIG. 6 shows the anti-rotation and overflow structure used with seal means of FIGS. 1 and 2. The structure comprises a pipe having a curved lower part `80 extending through the base of tank Shel-l 81 and an upright part 82 extending slidably through a vertical sleeve 83 in roof pontoon 84. Overiiow ports 85 are provided in pipe part 82 just above the desired maximum liquid level S6. The overflow ports are positioned to limit the uppermost positioning of the roof to insure adequate contact between the seal shoes -and the tank shell. The top of pipe part 82 is braced by transverse and diagonal lbeams -87 and 88 secured to and extending to an upright post 89 projecting above the upper edge of tank shell 81. rPipe 8), S2 is also supported and braced at the bottom by crossed webs 91 and 92 so that the pipe is rigid enough toA resist rotation of the roof. Skirt 98 depends from the periphery of main roof sheet 100, as in the previous forms, and sleeve 83 is extended below sheet 160, as at 99, to prevent the escape of product vapors, normally trapped near .the center of the roof sheet in case Iof minor tilting of the roof structure.

In the second form, as in the first, it will be possible for the roof to ride substantially above the level of the upper edge of the tank shell, bracing 87, S8 in FIG. 6 necessarily ybeing positioned high enough to permit this. ln general, the roof will rise and fall relative to the tank shell, as required by the varying quantities of fluid within the tank and the sealing bag will be caused by its novel supporting means to follow the roof.

A further advantage of the first yform is that the sealing means occupies a minimum of space within the tank, while providing a yspace 95 between the normal liquid level 96 and sealing diaphragm part 40 for the trapping of gases escaping from the surface of the liquid. Since the roof, in both forms, may be largely supported above .and outside the tank shell, the maximum capacity of the tank will be substantially greater than that of a tank of similar size using present types of seals.

The invention may be modied in various respects as Will occur to those skilled in the art, and the exclusive use of all modications as come within the scope of the `appended claims as contemplated.

I claim:

1. A iloating roof tank seal comprising a plate-like shoe for slidably engaging the tank wall, flexible diaphragm means secured to the upper part of said shoe for sealingly traversing the space between said shoe and portions of the roof abreast of said shoe, and a pair of vertically spaced apart leaf springs each with its foot end secured to the peripheral edge wall of the roof and extending upwardly land outwardly therefrom in a plane which is vertic-al and substantially perpendicular to said roof edge wall, the lower of said springs extending adjacent and slidably engaging the lower part of said shoe and being laterally stressed paral-lel to said vertical plane for urging the shoe outwardly against the tank wall, the upper rof said springs having an element secured to its mid portion which element extends adjacent the upper part of said shoe and is laterally stressed parallel to said vertical plane for urging said shoe against the tank wall.

2. A floating roof tank seal as described in claim 1 including a plurality of said shoes disposed around the tank and an annular series of said upper and lower leaf springs arranged about the tank and supporting and outwardly biasing said shoes.

3. In combination with a tank having a cylindrical wall and a floating roof therein with a cylindrical side wall facing and spaced from said tank wall, seal means between said walls comprising plate-like shoes arranged icircumferentially about and slidably engaging said tank wall, flexible diaphragm means secured to said shoes and sealingly traversing the space between said shoes and portions of said roof wall abreast of said shoes, lower and upper annular series of leaf springs all with their foot ends secured to said roof wall so that each spring of the upper series is vertically spaced above a spring of the lower series with the planes of action of such two springs lying in a single plane extending vertically and radially of the tank, said lower springs extending outwardly and upwardly to the vicinity of and slidably and resiliently ybearing against the lower portions of said shoes, said upper leaf springs extending outwardly and upwardly above said diaphragm means and each having an element secured to its mid portion and resiliently bearing against the upper portions of said shoes, and said roof extending substantially above said seal means whereby substantial portions of said roof project above the tank wall in the upper portion of the movement of said seal means along said tank wall.

4. The combination described in cl-aim 3 further including an upward extension on each of said upper springs and a weather shield supported on said extensions,

5. In a floating roof tank having a clearance space between the roof side wall and the tank wall, roof seal means in said space comprising flexible, imperforate sheeting sealingly traversing said space between said walls substantially below the top of said roof and movable vertically along said tank wall, Ia circumferential series of support straps projecting outwardly and upwardly yfrom said roof wall above said seal means and each having a bowed part near its upper extremity, means depending from mid portions of said straps below said bowed portions and secured to and supporting the tank wall engaging portions of said seal means, means biasing said seal means against said tank wall, and weather seal means carried on the upper extremities of said straps above said bowed portions and above said roof side wall and traversing said space, said straps projecting above said tank wall in the upper positions .of said roo-f and being of sutlicient rigidity to support at least the outer parts of said weather Seal means and said roof seal means, said straps being inclined inwardly above and below said bowed portions so as to slide along the tank wall and override discontinuities therein during ascent `of said roof and said bowed portions lbeing engageable by the upper edge of the tank wall during descent of said roof to ilex said straps inwardly and thereby conne said straps Within said tank wall.

6. Floating roof tank seal structure as described in claim 5 in which said means biasing said sheeting against said tank wall comprises resilient ybranch means projecting outwardly and downwardly from mid portions of said straps.

7. Floating roof tank seal structure as described in claim 5 in which said flexible sheeting -forms a toroidal bag and further including distending material in said bag and constituting the means urging said sheeting against said tank wall.

References Cited by the Examiner UNITED STATES PATENTS 1,592,524 7/1926 Holt 220-26 1,597,399 8/1926 Wilson 220-26 1,674,104 6/1928 Gallagher 220-26 2,478,422 8/ 1949 Plummer 220*26 2,600,237 6/ 1952 Graham 220-26 3,001,542 9/ 1961 Shepherd et al. 220-85 X 3,043,468 7/ 1962 Horner 220-26 FOREIGN PATENTS 1,196,283 5/1959 France. 1,026,239 3/ 1958 Germany.

888,831 2/1962 Great Britain.

THOMAS E. CONDON, Primary Examiner.

G. O. RALSTON, LOUIS G. MANCENE, Examiners. J. R. GARRETT, Assistant Examiner.

Claims (1)

1. 5. IN A FLOATING ROOF TANK HAVING A CLEARANCE SPACE BETWEEN THE ROOF SIDE WALL AND THE TANK WALL, ROOF SEAL MEANS IN SAID SPACE COMPRISING FLEXIBLE, IMPERFORATE SHEETING SEALINGLY TRAVERSING SAID SPACE BETWEEN SAID WALLS SUBSTANTIALLY BELOW THE TOP OF SAID ROOF AND MOVABLE VERTICALLY ALONG SAID TANK WALL, A CIRCUMFERENTIALLY SERIES OF SUPPORT STRAPS PROJECTING OUTWARDLY AND UPWARDLY FROM SAID ROOF WALL ABOVE SAID SEAL MEANS AND EACH HAVING A BOWED PART NEAR ITS UPPER EXTREMITY, MEANS DEPENDING FROM MID PORTIONS OF SAID STRAPS BELOW SAID BOWED PORTIONS AND SECURED TO AND SUPPORTING THE TANK WALL ENGAGING PORTIONS OF SAID SEAL MEANS, MEANS BIASING SAID SEAL MEANS AGAINST SAID TANK WALL, AND WHETHER SEAL MEANS CARRIED ON THE UPPER EXTREMITIES OF SAID STRAPS ABOVE SAID BOWED PORTIONS AND ABOVE SAID ROOF SIDE WALL AND TRAVERSING SAID SPACE, SAID STRAPS PROJECTING ABOVE SAID TANK WALL IN THE UPPER POSITIONS OF SAID ROOF AND BEING OF SUFFICIENT RIGIDITY TO SUPPORT AT LEAST THE OUTER PARTS OF SAID WEATHER SEAL MEANS AND SAID ROOF SEAL MEANS, SAID STRAPS BEING INCLINED INWARDLY ABOVE AND BELOW SAID BOWED PORTIONS SO AS TO SLIDE ALONG THE TANK WALL AND OVERRIDE DISCONTINUITIES THEREIN DURING ASCENT OF SAID ROOF AND SAID BOWED PORTIONS BEING ENGAGEABLE BY THE UPPER EDGE OF THE TANK WALL DURING DESCENT OF SAID ROOF TO FLEX SAID STRAPS INWARDLY AND THEREBY CONFINE SAID STRAPS WITHIN SAID TANK WALL.

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